Normal functioning mitochondria maintain an electrochemical gradient (ΔΨιη) across the inner membrane. The gradient is created through the efflux of H+ ions from the matrix to the intermembrane space, resulting in a pH and voltage gradient. The main driving force for the efflux of H+ ions is through the respiratory chain. However, several ion channels have been identified in the inner membrane, including the H+/K+ antiporter, the C17HC03~ antiporter, the Na7H+ exchanger and the uncoupling proteins, which presumably also help to maintain the ion flux balance (Brierley et a ly 1994; Garlid et al.y 1998). An important protein complex involved in the regulation of the H+ ion flux is the F0Fr ATPase/H+ pump. This pro tein complex normally converts ADP into ATP, and the driving force is the flux of H+ions from the intermembrane space into the matrix. However, when the H+ gra dient is low, the protein complex can work in the reverse direction, pumping H+ ions out from the matrix, whereby ATP is hydrolyzed into ADP.